Various apparatuses have been proposed that cyclically compress the heart (ventricles only) through the use of pressure changes of gases initially for the purpose of replacing open chest manual massage (directly massaging the heart by hand, a practice frequently used to resuscitate cardiac arrest patients) with machines, and then assisting the heart synchronous to heart beat following resumption of heart beat. The following provides a description of some typical examples of these apparatuses.
1) Apparatuses Using the Pericardium for Demonstrating Function
Examples of these apparatuses include an apparatus which feed a gas directly and cyclically into the pericardial cavity (using the pericardium as a balloon which can be inflated and deflated by feeding and discharging a gas thereinto) (refer to Adriano Bencini, et.al., Surgery, 1956, Vol. 39, No. 3, p. 375-); an apparatus in which a balloon is inserted into the pericardial cavity that can be inflated and deflated by feeding and discharging a gas into said balloon, that directly compresses the left ventricle with said balloon, and compresses the right ventricle by pinching the right ventricle between the left ventricle compressed with said balloon and the pericardium (the pericardium serves as a surface that reacts to the pressure resulting from inflation of said balloon) (a. an apparatus in which, although the balloon in this case only expands in the direction of compression of the left ventricle, with the portion that makes contact with the pericardium on the side of the left ventricle being lined with nylon mesh, the connection between said balloon and the device for feeding and discharging the gas is located at a single point on the surface of said balloon--refer to Gerald A. Jones, et.al., Dis. Chest, 1961, Vol. 9, p. 207-, and b. an apparatus is disclosed in which the inflation and deflation of said balloon can be synchronized with the heart beat--refer to Norman Rosenberg, et.al., Surgery, 1964, Vol. 56, No. 5, p. 980-); and, an apparatus in which balloons that can be inflated and deflated by feeding and discharging a gas thereinto are each sutured in position on the outer surface of the pericardium at locations geometrically corresponding to the left and right ventricles--refer to C. W. Hall, et.al., American Journal of Surgery, 1964, Vol. 108, p. 685-.
However, since these apparatuses result in excessive extension of the pericardium, there is the risk of causing its rupture. As these apparatuses are not even able to fulfill the objective of mechanical replacement of open chest manual massage, they have gradually fallen out of use (furthermore, as can be ascertained from their mode of use, these apparatuses require thoracotomy, and depending on the case, incision or puncture of the pericardium).
2) Apparatuses not Requiring Use of the Pericardium for Demonstrating Function
Apparatuses that attempt to solve the above-mentioned problems of the prior art are of a type referred to as apparatuses in which membrane member that can be expanded and contracted with the feeding and discharge of a gas into an inner space enclosed with said membrane member is arranged on the inner surface of a vessel able to contain both ventricles (said membrane member being respectively attached to said vessel entry and lower wall), and cyclical compression is applied to the heart by expanding and contracting said membrane member through the feeding and discharge of gas into the inner space enclosed with said membrane member with both ventricles suctioned and contained in said vessel (currently typically referred to as DMVA (direct mechanical ventricular actuation) (refer to Mark W. Wolcott et.al., Surgery, 1960, Vol. 48, No. 5, p. 903-; Theodor Kolobow et.al., Trans. Amer. Soc. Artif. Int. Organs Vol. XI, 1965, p. 57-; G. L. Anstadt et.al., Trans. Amer. Soc. Art if. Int. Organs Vol. XII, 1966, p. 72-; W. Rassman et.al., Journal of Thoracic and Cardiovascular Surgery, 1968, Vol. 56, No. 6, p. 858-; David Goldfarb, Prog. Cardiovasc. Dis., 1969, Vol. 12, No. 3, p. 221-; W. J. Kolff, Progress in Cardiovascular Diseases, 1969, Vol. XII, No. 3 page 243; Peter Schiff et.al., Trans. Amer. Soc. Artif. Int. Organs Vol. XV, 1969, p. 424-; and, Mark P. Anstadt et.al., Chest, 1991, Vol. 100, p. 86-; furthermore, an apparatus able to synchronize expansion and contraction of said membrane member with heart beat is disclosed in the reports of W. Rassman et. al. and Peter Schiff et.al. described above).
However, since these apparatuses involve the containment of both ventricles within a vessel for their application, they inevitably require both thoracotomy and incision of the pericardium, thus placing a considerable burden on patients. Consequently, they are not suitable for the purpose of routine cardiac assistance (assistance of cardiac contraction).
3) Non-Thoracotomy Types
In order to solve the above-mentioned problems of the prior art, an apparatus has been reported in which a vest-like air bladder is mounted on the chest to cyclically change the internal pressure of the thoracic cavity by compressing and releasing the thorax as a result of inflating and deflating said air bladder by the feeding and discharge of air into said air bladder (refer to Henry R. Halperin et.al., IEEE Transactions on Biomedical Engineering, 1987, Vol. BME-34, No. 9, p. 738-).
However, although this apparatus compresses the heart, since this force is transmitted from the thorax to the thoracic cavity and finally to the pericardium, force is required to oppose the resistance of each of the force transmitting sites in order to obtain reliable effects (assistance of cardiac contraction). In addition to the size of the gas feeding device being considerably large, compression of the thorax places a burden on patients (in terms of breathing effort in opposition to said compression as well as pain).